Digitally encoded video streams can be delivered to devices such as set-top boxes and televisions over a transmission channel of some type. A frame subjected to a transmission impediment may include one or more errors. In some types of frame encoding, such as Motion Picture Experts Group 2 (MPEG-2) video, frames are divided into blocks or macroblocks and compression is typically performed on a block-by-block basis in raster scan order. In such cases, when the decoder receives a video stream that has encountered an error that corrupts one macroblock, or even a few macroblocks, the decoder can recover at the start of the next slice, so the remainder of the frame can still be decoded. Other types of video encoding specifications, such as ITU H.264/MPEG AVC/MPEG-4 Part 10, often encode the frame as a single slice for better compression performance, so that any incurred error or loss to the coded frame can prevent the entire frame from being decoded. Furthermore, certain types of frames serve as reference pictures to other frames so any impaired portion of such frames may affect the decoding of these other frames.
Impairments are even more significant if the entire frame is unrecoverable or when an error in the frame affects a distant frame, either directly or via its propagation through other frames . . . . Thus, a need arises for these and other problems to be addressed.